Printheads for ink jet printers are precisely manufactured so that the components cooperate with an integral ink reservoir to deliver ink to an ink ejection device in the printhead to achieve a desired print quality. A major component of the printhead of an ink jet printer is the nozzle plate which contains ink supply channels, firing chambers and ports for expelling ink from the printhead.
Since the introduction of ink jet printers, nozzle plates have undergone considerable design changes in order to increase the efficiency of ink ejection and to decrease their manufacturing cost. Changes in the nozzle plate design continue to be made in an attempt to accommodate higher speed printing and higher resolution of the printed images.
Nozzle plates are complex structures which contain multiple ejection ports or nozzles for ejecting ink and channels for feeding ink from an ink reservoir to a firing chamber associated with the nozzle being used. Pressure is created in the firing chamber to expel a droplet of ink from the chamber through the nozzle to the substrate. The pressure also forces ink out of the supply channel and may affect the ink in the supply region or via feeding other supply channels and firing chambers.
Thermal ink jet printers use a plurality of resistance heating elements in the firing chambers to vaporize a component of the ink which then expands as a vapor bubble forcing ink out of the nozzle associated with the chamber. As the ink/vapor interface cools, the bubble begins to contract and finally collapses onto the heater surface. As the bubble collapses, the chamber refills by capillary action. As the chamber refills, the ink forms a meniscus which undergoes an oscillatory motion. The oscillatory motion of the meniscus tends to pull a small amount of air into the firing chamber and under certain conditions, the air may be trapped in the chamber. Trapped air may accumulate in the chamber after a number of firings. Once this happens, the performance of the nozzle degrades severely. Trapped air also act as a shock absorber which reduces the pumping action of the vapor bubble. If too much air is trapped in the firing chamber, it may push ink out of the ink supply channel or choke off the inlet of the channel thereby affecting the ability to refill the chamber. In addition to trapped air, debris in the ink may also effect the refilling of the firing chambers and thus the quality and efficiency of the ink ejected from the nozzles.
Methods for controlling the fluid refill rate of the firing chambers for an ink jet printhead are described in U.S. Pat. No. 4,882,595 to Trueba et al. As described in the '595 patent, cross-talk between the firing chambers may affect print speed and/or print quality. One method to reduce cross-talk is resistive decoupling which uses fluid friction present in the ink feed channel to dissipate energy associated with cross-talk surges. Another method uses inertial decoupling wherein long, slender feed channels are said to maximize the inertial aspect of the fluid entrance within the channels. However, both resistive decoupling and inertial decoupling were found to result in a longer settling time between firings of the nozzle. Another proposed solution to the problem was the use of localized constriction or a lumped resistance element at the entrance of the feed channel. Despite such proposals there continues to be a need for nozzle plate designs which improve the flow characteristics and refill speed of ink to the firing chambers.
It is an object of this invention, therefore, to provide improved nozzle plates for ink jet printheads.
It is another object of this invention to provide a method for reducing the interference between firing chambers of a thermal ink jet printhead.
It is a further object of this invention to provide nozzle plates for ink jet printers which possess improved ink flow characteristics under various operating conditions.
Still another object of the invention is to provide a method for manufacturing nozzle plates for ink jet printers.
A further object of the invention is to provide a method for laser ablating nozzle plates having improved ink flow characteristics.